The present invention relates to a remote control device adapted to control locking and unlocking, remotely from a vehicle such as an automobile vehicle, locks for doors and trunk of such vehicle.
Locks for doors and trunk of the automobile vehicle are often locked and unlocked by manually operating a key inserted thereinto. Recently, a remote control device has been developed which utilizes an electrical or optical remote control signal instead of the key to lock and unlock remotely from the automobile vehicle. Such remote control device comprises a receiver equipped on the automobile vehicle and a portable transmitter provided independently of the automobile vehicle.
A particular keyword information (key number) is assigned to each automobile vehicle in the form of a corresponding encoded information and a remote control signal in accordance with this encoded information is transmitted by a trigger operation from said transmitter. More specifically, the encoded information is directly modulated by the pulse number modulation technique to a corresponding pulse number of minimum width and the train of pulses thus obtained is electrically or optically transmitted as the remote control signal. As the optical remote control signal, infrared-ray energy has usually been used.
The receiver receives the remote control signal, demodulates or decodes it to regenerate the encoded information, compares this encoded information with an information previously stored by the lock and outputs an execution signal only when a result of this comparison is positive.
The door locks or the trunk lock are controlled by this execution so that the locked lock is unlocked and the unlocked lock is locked again. To prevent repeated locking and unlocking occurring due to repeated transmission of the remote control signal, there has been provided a countermeasure such that the one-way control from "locking" to "unlocking" or from "unlocking" to "locking" should be performed when said repeated transmission of the remote control signal is made within a predetermined time period.
The lock controlled in such a manner includes an electromagnetic driving mechanism adpated to be activated with said execution signal. Although the lock control is effected simultaneously with respect to all the door locks, different reception areas are assigned to respective remote control means associated with the door locks and with the trunk lock so that the door locks and the trunk lock may be separately controlled.
As indicated above, the remote control device of prior art utilizes a train of pulses having minimum width converted from the keyword information as the remote control signal and, as a result, is susceptive of malfunction due to influence of an electrical noise.
FIG. 5 illustrates by way of example a train of pulses transmitted as the remote control signal, in which each pulse width is 0.1 millisecond, synchronizing pulses P appear at an interval of 2.5 milliseconds, and the synchronizing pulses P having no signal pulse therebetween represent a code "0" while the synchronizing pulses P having a signal pulse P1 therebetween represent a code "1". Such remote control signal is code-regenerated on the basis of a count of the pulse number and, therefore, when an electrical noise pulse PX is generated as indicated by broken lines, the code "0" would be regenerated as the code "1", causing a malfunction.
The electrical noise is caused not only by operation of the device but also by the environmental factors and it has been difficult to overcome this perfectly.
Furthermore, in view of a fact that, with such remote control device, the transmitter is operated remotely from the automobile vehicle, the user often places reliance on function of the device and fails to confirm a result. A possible malfunction of the device would result in leaving the automobile vehicle with its doors and trunk unlocked and, with consequence, theft of goods loaded on the automobile vehicle or even of the automobile vehicle itself.